Apparatus and method for heating shaft furnaces with fuel gas

ABSTRACT

An improved fuel gas burner for vertical shaft furnaces has separately controllable fuel and air supply means for controlling combustion in addition to primary fuel and air supply means for supplying the main portion of these combustion gases.

United States Patent A Grimm et al.

14 1 Dec. 19, 1972 APPARATUS AND METHOD FOR HEATING SHAFT FURNACES WITH FUEL GAS Inventors: Werner Grimm; Karl H. Olschewski; Rolf E. Sack, all of Hamburg, Germany Assignee: Shell Oil Company, New York, NY.

Filed: Aug. 20, 1971 App]. No.: 173,464

Foreign Application Priority Data August 28, 1970 Germany ..P 20 42 838.0

US. Cl. "431/10, ins/2125135971 35.3,

431/174 Int. Cl ..F23k 1/00 Field of Search ...239/l32.3, 423', 431/174, 180, 431/8, l0

[56] References Cited UNITED STATES PATENTS 3,644,076 2/1972 Bagge ..239/132.3 x 3,308,869 3/1967 Livingston ..431/s x 3,147,795 9/1964 Livingston et 1. ..431/174 Primary Examiner-Meyer Perlin Assistant ExaminerW. C. Anderson Au0rneyHarold L. Denkler et al.

[57] ABSTRACT An improved fuel gas burner for vertical shaft furnaces has separately controllable fuel and air supply means for controlling combustion in addition to primary fuel and air supply means for supplying the main portion of these combustion gases.

3 Claims, 3 Drawing Figures PATENTEDUEEIQIHIZ 3,706,520

sum 1 or 2 f A/R AIR APPARATUS AND METHOD FOR HEATING SHAFT FURNACES WITII FUEL GAS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved apparatus for heating shaft furnaces, for example limebuming shaft kilns, with fuel gas by means of one or more vertical burners which are arranged in the interior of the furnace shaft in the lower part thereof. The invention also relates to a method of heating shaft furnaces by means of the said apparatus, in which the main portion of combustion air is passed for cooling purposes through the outer annular spaces of the burners and the hollow spaces of the burner supports, and is subsequently supplied to one or more outlet openings which are provided in known manner in the lower part of the furnace.

2. Description of the Prior Art The heating of lime-burning shaft kilns by means of fuel gas is known. Also known is the method of introducing the fuel gas into the interior of the furnace shaft, viz. in the lower third part thereof but above the furnace bottom, the combustion air being supplied directly to the furnace bottom. In this method the combustion air primarily serves for cooling the completely burnt part of the charge in front of the outlet openings. It is only further upwards from the fuel gas supply level that mixing takes place between the combustion air and the fuel gas distributed in the furnace charge, producing diffuse combustion which is vertically extended over part of the shaft height of the type desired for a uniform burning without local overheating (overbuming). This method calls for a special cooling of the apparatus through which the fuel gas is passed into the interior of the furnace charge. A burner has already been suggested which is arranged vertically on the furnace bottom and is cooled by the portion of combustion air which is supplied to a double outer annular space of the burner shaft.

The basic problem underlying the invention is to provide an attractive construction for the combustion zone and to make it controllable to such an extent that it can be adapted to fluctuating operating conditions, such as the composition of the charge which varies according to lumpiness, moisture content, etc. In this connection it is already known to arranged in the burner mentioned above a separate line for supplying a controlled portion of the combustion air which flows into the interior of the furnace near the fuel gas outlet.

SUMMARY OF THE INVENTION It has been found that the vertical extension of the combustion zone can be considerably better controlled while nevertheless the risk of local overheating is avoided by incorporating in this last mentioned burner a second separate supply line and distribution chamber for a controlled portion of the fuel gas. According to the invention the three distribution chambers thus available are arranged in such a manner that the chamber for the main portion of fuel gas is in the lowest position, above which the chamber for the controlled portion of the combustion air is situated while the chamber for the remaining portion of the fuel gas stream is above the latter chambeLSuitably the distribution chambers are so constructed that the horizonta] planes, in which the outlet openings lie, are arranged approximately -150 mm one above the other.

The main portion of combustion air flows in a known manner at the lower end of the vertical burner, i.e. near the furnace bottom, into the furnace shaft.

In larger furnaces, starting with a shaft diameter of about 3.50 m, one centrally arranged burner is no longer sufficient to ensure a uniform extension of the combustion zone over the entire cross-section area of the shaft. According to the invention, three or more of the said burners, spaced across the shaft section, are combined to form one heating apparatus. In this case it is advantageous for the supply lines of the individual burners to remain separately controllable.

Suitably, the burners of this voluminous apparatus are no longer arranged on the furnace bottom but on horizontal supports, which extend through furnace wall and furnace shaft. The supports are designed as hollow box-like elements. Suitably, the lines for the main portion and the remaining portion of the fuel gas and the controlledportion of the combustion'air pass through the hollow space of the supports. It is advantageous to pass the main portion of combustion air through the hollow space round the lines, as a result of which the support is cooled.

In heating a shaft furnace by means of the said apparatus the following procedure is advantageously followed: the main portion of combustion air for each burner is supplied through the relevant line, passed in a known manner through the outer annular spaces of the burner and subsequently returned to the atmosphere through the hollow space of the support. Consequently, the customary outlet opening at the lower end of the burner when single burners are used is omitted; the outer annular space of the burner is contiguous with the hollow space of the support. The burners can be operated consecutively with the same air stream (series connection); however, they are conveniently connected in parallel, either in groups or individually, the returning air streams then being combined. Outside the furnace these air streams are subsequently passed to one or more outlet openings which are provided in the furnace bottom and are covered in known manner with protective caps. If this procedure is followed, burners of smaller overall height will suffice. A corresponding arrangement of the supports will provide adequate space underneath the combustion zone, in which the completely burned charge is cooled by the combustion air rising from the furnace bottom.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 3 shows a hollow support in (vertical) cross-sec- IIOII.

DESCRIPTION OF A PREFERRED EMBODIMENT I In the burner shown in FIG. 1 the horizontal supply lines 2, 5, 8 and 12 for the individual streams of air and fuel are arranged concentrically in'the same way as in the vertical part of the burner. They run either underneath the furnace bottom or in a hollow support (not shown) to the control valveson the lower right, which are readily accessible. The main portion of combustion air enters at l and passes through the annular space between tubes 2 and 5..At the upper end of the tube 2, the stream is deflected and passes through the outer annular space between the tube 2 and a tubular shell 3. At the lower end 25 of the outer annular space the combustion air either flows out into the furnace shaft or enters the hollow space of the support.

The main portion of fuel gas enters at 4 and passes through the annular space between the tubes 5 and 8 to a distribution chamber 6 and through outlet openings 7 into the furnace shaft. A portion of the combustion air passes via a connection 26 into the annular space between the tube 8 and a conduit 12, and enters a distribution chamber 9 from where it flows via its outlet openings 10 into the furnace shaft. A portion of the fuel gas is introduced at 11 and passes through the conduit 12 into a distribution chamber 14 and flows out through an opening 15 thereof.

A plurality of triangular connecting plates 16 a, b, c

y are welded between the tubular shell 3 and the flange at the lower end thereof and also, sloping to the nearest wall, on the covers of the distribution chambers, in order to reinforce the construction. The spaces between the connecting plates are filled with a fireproof ramming mass to form conical surfaces.

In FIG. 2 the reference numeral 17 designates the furnace wall with the fireproof inner lining. Two hollow supports 18 are passed transversely through the furnace shaft and, within the furnace carry two burners 19 each. This embodiment of the apparatus is preferred in that it reduces the free cross-sectional area of the shaft to a lesser extent than for instance a cross-shaped or a star-shaped arrangement of the supports.

The hollow support shown in F IG. 3 is formed from a double T-beam 20, side plates 21 and a cover plate 22. On the cover plate metal strips 23 form a ridge along which the downward moving furnace charge slides. The supply lines provided in the hollow space are arranged concentrically, as shown in FIG. 1, and are designated by the same reference numerals.

We claim as our invention:

1. An improved shaft-furnace fuel gas burner of the type having a central supply line and distribution chamber for a first portion of combustion air; an annular supply line and annular distribution chamber for fuel gas surrounding the central air supply line; and, surrounding the annular fuel gas supply line, an outer supply line comprising two adjacent, concentric annular passageways one surrounding the other for a second portion of combustion air, the two passageways being in fluid communication at the top portions thereof whereby air may be passed upwardly through the innermost of the passageways to cool the fuel gas in the annular fuel gas supply line and then downwardly away from the top of the burner to a point of combustion air introduction near the bottom of the furnace, the improvement comprising:

a second supply line and a second distribution chamber for fuel gas, and means for adjusting the supply of fuel to said second fuel supply line to control the combustion zone of the burner. 2. The burner of claim 1 wherein, when the burner is 3. A method for heating vertical shaft furnaces with fuel gas comprising the steps of:

introducing a combustion control portion of fuel gas into the furnace through a central conduit in a burner;

introducing a combustion control portion of air into the furnace through an annular discharge chamber of the burner positioned below the point of introduction of the combustion control portion of fuel gas;

introducing a main portion of fuel gas into the furnace through an annular fuel-discharge chamber of the burner positioned below the point of introduction of the combustion control portion of air;

passing a main portion of air through the burner to cool the main portion of fuel gas before it enters the annular fuel-discharge chamber;

conducting the main portion of air to a point adjacent the furnace bottom; and

introducing the main portion of combustion air into the furnace adjacent the bottom thereof and below the burner whereby the main portion of air rises through the furnace and diffusely combines with fuel gas introduced into the furnace through the burner to heat the furnace. 

1. An improved shaft-furnace fuel gas burner of the type having a central supply line and distribution chamber for a first portion of combustion air; an annular supply line and annular distribution chamber for fuel gas surrounding the central air supply line; and, surrounding the annular fuel gas supply line, an outer supply line comprising two adjacent, concentric annular passageways one surrounding the other for a second portion of combustion air, the two passageways being in fluid communication at the top portions thereof whereby air may be passed upwardly through the innermost of the passageways to cool the fuel gas in the annular fuel gas supply line and then downwardly away from the top of the burner to a point of combustion air introduction near the bottom of the furnace, the improvement comprising: a second supply line and a second distribution chamber for fuel gas, and means for adjusting the supply of fuel to said second fuel supply line to control the combustion zone of the burner.
 2. The burner of claim 1 wherein, when the burner is vertically disposed in the shaft furnace, the annular discharge chamber for fuel gas is positioned below the distribution chamber for the first portion of combustion air and wherein the second distribution chamber for fuel gas is positioned above the distribution chamber for the first portion of combustion air, the second fuel supply line being located within the central air supply line and passing upwardly through the distribution chamber for the first portion of combustion air to the second distribution chamber for fuel gas.
 3. A method for heating vertical shaft furnaces with fuel gas comprising the steps of: introducing a combustion control portion of fuel gas into the furnace through a central conduit in a burner; introducing a combustion control portion of air into the furnace through an annular discharge chamber of the burner positioned below the point of introduction of the combustion control portion of fuel gas; introducing a main portion of fuel gas into the furnace through an annular fuel-discharge chamber of the burner positioned below the point of introduction of the combustion control portion of air; passing a main portion of air through the burner to cool the main portion of fuel gas before it enters the annular fuel-discharge chamber; conducting the main portion of air to a point adjacent the furnace bottom; and introducing the main portion of combustion air into the furnace adjacent the bottom thereof and below the burner whereby the main portion of air rises through the furnace and diffusely combines with fuel gas introduced into the furnace through the burner to heat the furnace. 